Three-Dimensional Structural Modeling of Displacements of the Edwards Aquifer Within the Balcones Fault Zone in Northern Bexar County, Texas

James C. Cole and Michael P. Pantea
U.S. Geological Survey, Denver Colorado

Drill-hole and outcrop data for hydrologically distinct subunits of the Edwards aquifer system are used as control for three-dimensional modeling of fault displacements in northern Bexar County adjacent to the San Antonio metropolitan area. The model allows detailed examination of the displacement patterns along strands of the Balcones fault zone. These patterns, in turn, allow the evaluation of the extent of dislocation of the whole aquifer and the analysis of the juxtaposition of hydrostratigraphic units between individual fault blocks. This analysis suggests new ways of thinking about the evolution of permeability in the aquifer, and the impacts of fault displacement history on formation of high-permeability zones in the system.

AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004